1 /* Target-dependent code for GNU/Linux on Alpha. 2 Copyright 2002, 2003 Free Software Foundation, Inc. 3 4 This file is part of GDB. 5 6 This program is free software; you can redistribute it and/or modify 7 it under the terms of the GNU General Public License as published by 8 the Free Software Foundation; either version 2 of the License, or 9 (at your option) any later version. 10 11 This program is distributed in the hope that it will be useful, 12 but WITHOUT ANY WARRANTY; without even the implied warranty of 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 GNU General Public License for more details. 15 16 You should have received a copy of the GNU General Public License 17 along with this program; if not, write to the Free Software 18 Foundation, Inc., 59 Temple Place - Suite 330, 19 Boston, MA 02111-1307, USA. */ 20 21 #include "defs.h" 22 #include "frame.h" 23 #include "gdb_assert.h" 24 #include "osabi.h" 25 26 #include "alpha-tdep.h" 27 28 /* Under GNU/Linux, signal handler invocations can be identified by 29 the designated code sequence that is used to return from a signal 30 handler. In particular, the return address of a signal handler 31 points to a sequence that copies $sp to $16, loads $0 with the 32 appropriate syscall number, and finally enters the kernel. 33 34 This is somewhat complicated in that: 35 (1) the expansion of the "mov" assembler macro has changed over 36 time, from "bis src,src,dst" to "bis zero,src,dst", 37 (2) the kernel has changed from using "addq" to "lda" to load the 38 syscall number, 39 (3) there is a "normal" sigreturn and an "rt" sigreturn which 40 has a different stack layout. 41 */ 42 43 static long 44 alpha_linux_sigtramp_offset_1 (CORE_ADDR pc) 45 { 46 switch (alpha_read_insn (pc)) 47 { 48 case 0x47de0410: /* bis $30,$30,$16 */ 49 case 0x47fe0410: /* bis $31,$30,$16 */ 50 return 0; 51 52 case 0x43ecf400: /* addq $31,103,$0 */ 53 case 0x201f0067: /* lda $0,103($31) */ 54 case 0x201f015f: /* lda $0,351($31) */ 55 return 4; 56 57 case 0x00000083: /* call_pal callsys */ 58 return 8; 59 60 default: 61 return -1; 62 } 63 } 64 65 static LONGEST 66 alpha_linux_sigtramp_offset (CORE_ADDR pc) 67 { 68 long i, off; 69 70 if (pc & 3) 71 return -1; 72 73 /* Guess where we might be in the sequence. */ 74 off = alpha_linux_sigtramp_offset_1 (pc); 75 if (off < 0) 76 return -1; 77 78 /* Verify that the other two insns of the sequence are as we expect. */ 79 pc -= off; 80 for (i = 0; i < 12; i += 4) 81 { 82 if (i == off) 83 continue; 84 if (alpha_linux_sigtramp_offset_1 (pc + i) != i) 85 return -1; 86 } 87 88 return off; 89 } 90 91 static int 92 alpha_linux_pc_in_sigtramp (CORE_ADDR pc, char *func_name) 93 { 94 return alpha_linux_sigtramp_offset (pc) >= 0; 95 } 96 97 static CORE_ADDR 98 alpha_linux_sigcontext_addr (struct frame_info *next_frame) 99 { 100 CORE_ADDR pc; 101 ULONGEST sp; 102 long off; 103 104 pc = frame_pc_unwind (next_frame); 105 frame_unwind_unsigned_register (next_frame, ALPHA_SP_REGNUM, &sp); 106 107 off = alpha_linux_sigtramp_offset (pc); 108 gdb_assert (off >= 0); 109 110 /* __NR_rt_sigreturn has a couple of structures on the stack. This is: 111 112 struct rt_sigframe { 113 struct siginfo info; 114 struct ucontext uc; 115 }; 116 117 offsetof (struct rt_sigframe, uc.uc_mcontext); 118 */ 119 if (alpha_read_insn (pc - off + 4) == 0x201f015f) 120 return sp + 176; 121 122 /* __NR_sigreturn has the sigcontext structure at the top of the stack. */ 123 return sp; 124 } 125 126 static void 127 alpha_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch) 128 { 129 struct gdbarch_tdep *tdep; 130 131 /* Hook into the DWARF CFI frame unwinder. */ 132 alpha_dwarf2_init_abi (info, gdbarch); 133 134 /* Hook into the MDEBUG frame unwinder. */ 135 alpha_mdebug_init_abi (info, gdbarch); 136 137 tdep = gdbarch_tdep (gdbarch); 138 tdep->dynamic_sigtramp_offset = alpha_linux_sigtramp_offset; 139 tdep->sigcontext_addr = alpha_linux_sigcontext_addr; 140 tdep->pc_in_sigtramp = alpha_linux_pc_in_sigtramp; 141 tdep->jb_pc = 2; 142 tdep->jb_elt_size = 8; 143 } 144 145 void 146 _initialize_alpha_linux_tdep (void) 147 { 148 gdbarch_register_osabi (bfd_arch_alpha, 0, GDB_OSABI_LINUX, 149 alpha_linux_init_abi); 150 } 151